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Home Q & A Board Science-Related Homework Help Mathematics
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!JRon@n !JRon@n
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11 years ago
I'm pretty lost. Here's an example problem. Please show and explain steps. Thank you.

4x^2+9y^2=72
x-y^2=-1
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rjframerjframe
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11 years ago
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#2
11 years ago
Problems of this type which involves different degree of variables is done using elimination method

4x^2+9y^2=72 --------------------------1)
x-y^2=-1-------------------------------------2)
Noticing that both first and second equation contain second degree y variable we will eliminate that first

from 2 we have
         y^2  = x +1
substituting that in 1 we have

    4x^2 + 9(x+1)  = 72

   4x^2 +9x+9  = 72
  4x^2+9x -63  = 0

  so x =   -b +/= sqrt(b^2 - 4ac)  /2a

      x  =   - 9  +/-  sqrt( 81 - 4*4*(-9) /  8

              = -9+/- 33 /  8   = 3 or -21/4

y^2  = x +1 so

   y^2  = 3 +1      or      -21/4 +1

   y^2 = 4          or -17/4  | y becomes imaginary neglecting that value

   we have (3,2)  or  (3.-2) as answer
you can substitute and check the answer
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